It is desirable to be able to sense two components of a planar field using batch fabricated devices on the same substrate without the need of sawing and packaging. Currently available technology solves this problem by annealing-in orthogonal Pinned Layer/Reference Layer (PL/RL) magnetization directions on neighboring tunnel junctions.
Magnetic tunnel junctions have high magnetoresistance ratio (i.e., (Rmax−Rmin)/Rmin=ΔR/R) on the order of 100's of % and are currently used to measure moderate to high levels of magnetic fields. Magnetic tunnel junctions also have a high 1/f noise. The high noise density at low frequencies prevents the use of magnetic tunnel junctions for measuring small levels of magnetic field at frequencies less than of the order of a kHz.